Electrolytic composite anode and connector



Jax-3 B70 n. GELD g ELECTROLYTICCOMPOSITE ANODE AND CONNECTOR Filed may 31, 1.967

INVENTOR. [5mn/e5 GEL 0 United States Patent O 3,488,274 ELECTROLYTIC COMPOSITE ANODE AND CONNECTOR Isidore Geld, Flushing, N.Y., assigner to the United States of America as represented by the Secretary of the Navy Filed May 31, 1967, Ser. No. 643,326 Int. Cl. C23f 13/00 U.S. Cl. 204-196 3 Claims ABSTRACT F THE DISCLOSURE An impressed current cathodic protection device which includes a structure having high anodic electrolytic resistance and low electronic pressure resistance. One face of the structure is coated with platinum which is the effective anode and the structure disposed in a dielectric housing except for the one face and a portion of the opposite face. The anode and the housing are positioned in an aperture in the hull of a ship below the waterline With the coated surface facing outwardly and flush with the hull surface. The housing abuts the aperture walls while a stem portion is threaded through the housing or welded so as to form a pressure contact with the anode structure. A non-electrically conducting stuffing gland provides a watertight seal between the stem and the aperture walls. Current passing between the stem-anode and the ships hull provides cathodic protection for the metal hull.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the pay,- ment of any royalties thereon or therefor.

BACKGROUND OF INVENTION The present invention relates to cathodic protection of metallic ships hulls in sea Water and more particularly to an anode structure for an active cathodic protection system aboard a high speed ship and which may be readily removed and replaced without the necessity of drydocking the ship. Corrosion of ships hulls exposed to sea water is due to galvanic action which involves the genera tion of an electric potential between two metals or between different sections of a metal surface having different oxidation-reduction potentials.

Present cathodic protection systems may be classified as being of two types, an active and a sacrificial system. These systems involve on the one hand galvanic or sacricial anodes and on the other D.C. impressed currents. The impressed current or active type is becoming increasingly useful on hulls of active ships due to the smaller bulk and weight of the anode materials employed, In the active system, the ships hull is serially connected through the sea water (electrolyte) to an anode insulated from the hull and a D.C. current passed therethrough. This passage of current results in a polarization effect which acts to block the adverse effects of the galvanic action on a ships hull.

All of the present active systems which employ impressed current anodes are deficient in at least one respect. Anodes which are employed aboard active ships may protude from the hull and become damaged or broken off by mechanical inpact and/or high speed. In order to replace an anode, it is necessary either to remove and replace the anode with its electrical cable and connection or to replace the entire structure. In either case this generally necessitates the drydocking of the ship itself. It is clear under these circumstances that if minimizing damage to the anode and replacement thereof when required, carried out by a diver while the ship is in the water, the savings in both time, expense, and ships availability would be substantial.

Present anodes have a radius much larger than the connector and require at least a large, equal radius insulator between the anode and hull.

SUMMARY OF THE INVENTION The general purpose of this invention is to provide a readily replaceable anode for an impressed current cathodic device which is mounted fiush with the ships hull so as to reduce damage and cavitation. Additionally the anode is provided with a platinum coating on its outer face and encased in a dielectric holder which alSo supports a stem connector in physical contact with the opposite face of the anode. Both the anode and the stern are made of a material which has a high anodic electrolytic resistance in sea water and a low electronic resistance on pressure contact with another conductor. The holder is disposed and supported entirely within opening in the ships hull.

An object of this present invention is to provide a readily replaceable anode and/or holder for use on high speed ships and with an active cathodic protection system.

Another object of this invention is to provide a simple, reliable, inexpensive, practical and efficient cathodic protection system whose anode may be readily replaced by a diver who can be relatively unskilled in the electrical art without endangering the ships electrical svstem.

Still another object is to provide an anode that is an integral part of the throughhull connection, is flush with the hull surface, requires no more labor to install than that for installing a stuffing gland, and requires no mechanical fastening directly to the hull.

Other objects and advantages will 'appear from the following description of an example of the invention, and the novel features will be particularly pointed Out in the appended claims.

In the accompanying drawings:

FIG. l is a cross-sectional view of an embodiment made in accordance with the principles of this invention, and

FIGS. la and b are cross-sectional views of modified portions of the embodiment of FIG. 1.

DESCRIPTION OF 'PHE PREFERRED EMBODIMENT In the illustrated embodiment of FIG. 1, the hull 10 of a high speed ship such as a hydrofoil is provided, below the waterline, with a circular opening 11 extending therethrough and joined by welding to a cylindrical flange 12 which can be considered an extension thereof. lf the hull is of sufficient thickness this flange is not necessary for the purposes of this embodiment. Disposed about the opening 11 and affixed to the ships hull is a dielectric shield 13 which may be of any thin dielectric material that is unaffected by sea water or electrolysis products such as neoprene. The shield extends well beyond the outer peripheral edge of the opening in order that the distribution of the current will cover as large an area as possible surrounding the opening into which an anode iS placed.

The anode structure 14 is of a generally cylindrical form and of an electrically conductive material which has a high anodic electrolytic resistance in water, a high resistance to chemical deterioration, and a low resistance on pressure contact with an electronic conductor, examples of which are tantalum and titanium. The anode may include integral therewith a depending stem 15 of the same material as the anode portion 14. The anode is disposed in the hull opening 11 with the stem 15 extending inwardly of the hull while the outward face of the anode is coated or cladded with a layer of platinum 16. The upper or outer clad surface is position flush with the hull.

The anode, except for the clad surface and a portion of the stem are confined within a surrounding electrically insulating means or as illustrated a housing 17 whose inner surfaces abut and conform to the anode and whose outer surface tightly abuts the inner walls of the hull opening 11. The housing 17 serves to confine and position the `anode as well as to electrically insulate the anode from the hull and to prevent entry of water past the anode into the ship. The lower wall 18 of the housing is provided with an aperture 19 whose inner wall is threaded to mate with threads provided on the outer surface f the upper portion of stem 15. This structural arrangement limits any relative movement between the housing 17 and the anode-stem combination when the anode is seated in the housing and the stem threaded to the housing.

Disposed inwardly of the housing between the stem and the hull wall or penetration flange is a stufng gland 20 which may be of any standard construction presently available on the market. The gland is represented as shown since many types are available and suitable for the purposes of maintaining the watertight integrity of the hull and to limit movement of the stem-anode combination. The lower or inner portion 21 of the stern extends well within the ship and there mates with a detachable electrical connector 22 which is connected by cable 23 to the positive terminal 24 of a D.C. power supply 25. The negative terminal 26 of the supply is connected via cable 27 to the ships hull as at 28. Clearly, with this physical arrangement, replacement of the anode is a relatively simple matter and can be accomplished from the outside 0f the ship.

Since the watertightness of the hull would be lost if both the anode and the stem were simultaneously removed, separate components are illustrated in FIGS. 1a and b. In FIG. la the stem 15a is threaded into the housing 17 so as to tightly abut the anode and thereby form a low resistance electronic contact therewith. When the anode 14a is removed (Without the housing 17) the outside water will not pass the remaining stem and gland 20. Moreover, the power supply will not be shorted to the incoming sea water contacting the stem since the tantalum or titanium provides a high anodic electrolytic resistance. As an additional alternative and illustrated in FIG. 1b, a platinum-clad tantalum cap 16b may be substituted for the coated portion of the anode and aixed to the anode as by threading into a mating thread 29 within the anode 14b which is integral with the stern 15b. Locking structures can be incorporated in accordance with standard practice.

With l0 volts applied potential (normally encountered in ship service), the current output from a platinum clad anode of approximately 2 square inches is about 2.5 amperes, which will provide adequate protection for a hydrofoil. Two to four such anodes will suffice for a typical PC class ship or any boat with a relatively small underwater surface area. Electrochemical deterioration of the platinum at these current densities is negligible. Further the anode structure described requires no more labor to install than that necessary to install a stuing gland and yet does not necessitate any mechanical fastening directly to the ships hull. The flush mounting helps reduce damage by impact and does not interfere with the high speed hydrodynamics. Cavitation damage to the platinum is not a problem on a hydrofoil since vigorous gas evolution at the anode provides a gas cushion which prevents possible damage.

It will be 'understood 'that various changes in the details, materials, and arrangements of parts (and steps), which have -been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art 'within the principle and scope of the invention as expressed in the appended claims.

I claim:

1. An impressed current cathodic protection system for a high velocity metal hulled ship having a direct current supply source carried by said ship and having the negative terminal of said source connected to said metal hull, which comprises:

an opening through said hull below the waterline,

a dielectric sheath aixed to said hull in the area proximate and spaced from said opening,

, an anode of a material having a high anodic electrolytic resistance in sea water and low electronic resistance on pressure contact with another conductor,

said anode having one surface thereof clad with platinum and disposed in said opening with said clad surface facing outwardly of and 'ush with said hull, and

electrically insulating means disposed about said anode and between said anode and the walls of said opening, and having a threaded passageway on the portion thereof opposite said clad surface,

A stern of the same material as said anode being threaded into said passageway and in abutting relation with the rear surface of said anode,

whereby when the positive terminal of said source is connected to said stem said system will provide active cathodic protection for said hull.

2. The anode structure according to claim 1 wherein said anode comprises a pair of separable parts:

a main anode part, and

a platinum coated cap portion detachably affixed to said main anode part.

3. The anode structure according to claim 2 wherein r said cap portion is threaded into said main anode part.

References Cited UNITED STATES PATENTS 2,805,987 9/1957 Thorn et al 204-197 3,081,252 3/1963 Preiser et al. 204-196 3,133,872 5/1964 Miller et al 204-196 3,133,873 5/l964 Miller et al. 204-196 JOHN H. MACK, Primary Examiner T. TUNG, Assistant Examiner U.S. Cl. X.R. 

